diff --git a/components/style/values/specified/calc.rs b/components/style/values/specified/calc.rs
new file mode 100644
index 00000000000..4f49df256e7
--- /dev/null
+++ b/components/style/values/specified/calc.rs
@@ -0,0 +1,547 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+//! [Calc expressions][calc].
+//!
+//! [calc]: https://drafts.csswg.org/css-values/#calc-notation
+
+use app_units::Au;
+use cssparser::{Parser, Token};
+use parser::ParserContext;
+use std::ascii::AsciiExt;
+use std::fmt;
+use style_traits::ToCss;
+use values::{CSSInteger, CSSFloat, HasViewportPercentage};
+use values::specified::{Angle, Time};
+use values::specified::length::{FontRelativeLength, NoCalcLength, ViewportPercentageLength};
+
+/// A node inside a `Calc` expression's AST.
+#[derive(Clone, Debug)]
+pub enum CalcNode {
+    /// `<length>`
+    Length(NoCalcLength),
+    /// `<angle>`
+    Angle(Angle),
+    /// `<time>`
+    Time(Time),
+    /// `<percentage>`
+    Percentage(CSSFloat),
+    /// `<number>`
+    Number(CSSFloat),
+    /// An expression of the form `x + y`
+    Sum(Box<CalcNode>, Box<CalcNode>),
+    /// An expression of the form `x - y`
+    Sub(Box<CalcNode>, Box<CalcNode>),
+    /// An expression of the form `x * y`
+    Mul(Box<CalcNode>, Box<CalcNode>),
+    /// An expression of the form `x / y`
+    Div(Box<CalcNode>, Box<CalcNode>),
+}
+
+/// An expected unit we intend to parse within a `calc()` expression.
+///
+/// This is used as a hint for the parser to fast-reject invalid expressions.
+#[derive(Clone, Copy, PartialEq)]
+pub enum CalcUnit {
+    /// `<number>`
+    Number,
+    /// `<integer>`
+    Integer,
+    /// `<length>`
+    Length,
+    /// `<length> | <percentage>`
+    LengthOrPercentage,
+    /// `<angle>`
+    Angle,
+    /// `<time>`
+    Time,
+}
+
+/// A struct to hold a simplified `<length>` or `<percentage>` expression.
+#[derive(Clone, PartialEq, Copy, Debug, Default)]
+#[cfg_attr(feature = "servo", derive(HeapSizeOf))]
+#[allow(missing_docs)]
+pub struct CalcLengthOrPercentage {
+    pub absolute: Option<Au>,
+    pub vw: Option<CSSFloat>,
+    pub vh: Option<CSSFloat>,
+    pub vmin: Option<CSSFloat>,
+    pub vmax: Option<CSSFloat>,
+    pub em: Option<CSSFloat>,
+    pub ex: Option<CSSFloat>,
+    pub ch: Option<CSSFloat>,
+    pub rem: Option<CSSFloat>,
+    pub percentage: Option<CSSFloat>,
+    #[cfg(feature = "gecko")]
+    pub mozmm: Option<CSSFloat>,
+}
+
+impl HasViewportPercentage for CalcLengthOrPercentage {
+    fn has_viewport_percentage(&self) -> bool {
+        self.vw.is_some() || self.vh.is_some() ||
+        self.vmin.is_some() || self.vmax.is_some()
+    }
+}
+
+impl ToCss for CalcLengthOrPercentage {
+    #[allow(unused_assignments)]
+    fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
+        let mut first_value = true;
+        macro_rules! first_value_check {
+            () => {
+                if !first_value {
+                    try!(dest.write_str(" + "));
+                } else {
+                    first_value = false;
+                }
+            };
+        }
+
+        macro_rules! serialize {
+            ( $( $val:ident ),* ) => {
+                $(
+                    if let Some(val) = self.$val {
+                        first_value_check!();
+                        try!(val.to_css(dest));
+                        try!(dest.write_str(stringify!($val)));
+                    }
+                )*
+            };
+        }
+
+        try!(dest.write_str("calc("));
+
+        serialize!(ch, em, ex, rem, vh, vmax, vmin, vw);
+
+        #[cfg(feature = "gecko")]
+        {
+            serialize!(mozmm);
+        }
+
+        if let Some(val) = self.absolute {
+            first_value_check!();
+            try!(val.to_css(dest));
+        }
+
+        if let Some(val) = self.percentage {
+            first_value_check!();
+            try!(write!(dest, "{}%", val * 100.));
+        }
+
+        write!(dest, ")")
+    }
+}
+
+impl CalcNode {
+    /// Tries to parse a single element in the expression, that is, a
+    /// `<length>`, `<angle>`, `<time>`, `<percentage>`, according to
+    /// `expected_unit`.
+    ///
+    /// May return a "complex" `CalcNode`, in the presence of a parenthesized
+    /// expression, for example.
+    fn parse_one(
+        context: &ParserContext,
+        input: &mut Parser,
+        expected_unit: CalcUnit)
+        -> Result<Self, ()>
+    {
+        match (try!(input.next()), expected_unit) {
+            (Token::Number(ref value), _) => Ok(CalcNode::Number(value.value)),
+            (Token::Dimension(ref value, ref unit), CalcUnit::Length) |
+            (Token::Dimension(ref value, ref unit), CalcUnit::LengthOrPercentage) => {
+                NoCalcLength::parse_dimension(context, value.value, unit)
+                    .map(CalcNode::Length)
+            }
+            (Token::Dimension(ref value, ref unit), CalcUnit::Angle) => {
+                Angle::parse_dimension(value.value,
+                                       unit,
+                                       /* from_calc = */ true)
+                    .map(CalcNode::Angle)
+            }
+            (Token::Dimension(ref value, ref unit), CalcUnit::Time) => {
+                Time::parse_dimension(value.value,
+                                      unit,
+                                      /* from_calc = */ true)
+                    .map(CalcNode::Time)
+            }
+            (Token::Percentage(ref value), CalcUnit::LengthOrPercentage) => {
+                Ok(CalcNode::Percentage(value.unit_value))
+            }
+            (Token::ParenthesisBlock, _) => {
+                input.parse_nested_block(|i| {
+                    CalcNode::parse(context, i, expected_unit)
+                })
+            }
+            (Token::Function(ref name), _) if name.eq_ignore_ascii_case("calc") => {
+                input.parse_nested_block(|i| {
+                    CalcNode::parse(context, i, expected_unit)
+                })
+            }
+            _ => Err(())
+        }
+    }
+
+    /// Parse a top-level `calc` expression, with all nested sub-expressions.
+    ///
+    /// This is in charge of parsing, for example, `2 + 3 * 100%`.
+    fn parse(
+        context: &ParserContext,
+        input: &mut Parser,
+        expected_unit: CalcUnit)
+        -> Result<Self, ()>
+    {
+        let mut root = Self::parse_product(context, input, expected_unit)?;
+
+        loop {
+            let position = input.position();
+            match input.next_including_whitespace() {
+                Ok(Token::WhiteSpace(_)) => {
+                    if input.is_exhausted() {
+                        break; // allow trailing whitespace
+                    }
+                    match input.next()? {
+                        Token::Delim('+') => {
+                            let rhs =
+                                Self::parse_product(context, input, expected_unit)?;
+                            let new_root =
+                                CalcNode::Sum(Box::new(root), Box::new(rhs));
+                            root = new_root;
+                        }
+                        Token::Delim('-') => {
+                            let rhs =
+                                Self::parse_product(context, input, expected_unit)?;
+                            let new_root =
+                                CalcNode::Sub(Box::new(root), Box::new(rhs));
+                            root = new_root;
+                        }
+                        _ => return Err(()),
+                    }
+                }
+                _ => {
+                    input.reset(position);
+                    break
+                }
+            }
+        }
+
+        Ok(root)
+    }
+
+    /// Parse a top-level `calc` expression, and all the products that may
+    /// follow, and stop as soon as a non-product expression is found.
+    ///
+    /// This should parse correctly:
+    ///
+    ///     * `2`
+    ///     * `2 * 2`
+    ///     * `2 * 2 + 2` (but will leave the `+ 2` unparsed).
+    ///
+    fn parse_product(
+        context: &ParserContext,
+        input: &mut Parser,
+        expected_unit: CalcUnit)
+        -> Result<Self, ()>
+    {
+        let mut root = Self::parse_one(context, input, expected_unit)?;
+
+        loop {
+            let position = input.position();
+            match input.next() {
+                Ok(Token::Delim('*')) => {
+                    let rhs = Self::parse_one(context, input, expected_unit)?;
+                    let new_root = CalcNode::Mul(Box::new(root), Box::new(rhs));
+                    root = new_root;
+                }
+                // TODO(emilio): Figure out why the `Integer` check.
+                Ok(Token::Delim('/')) if expected_unit != CalcUnit::Integer => {
+                    let rhs = Self::parse_one(context, input, expected_unit)?;
+                    let new_root = CalcNode::Div(Box::new(root), Box::new(rhs));
+                    root = new_root;
+                }
+                _ => {
+                    input.reset(position);
+                    break
+                }
+            }
+        }
+
+        Ok(root)
+    }
+
+    /// Tries to simplify this expression into a `<length>` or `<percentage`>
+    /// value.
+    fn to_length_or_percentage(&self) -> Result<CalcLengthOrPercentage, ()> {
+        let mut ret = CalcLengthOrPercentage::default();
+        self.add_length_or_percentage_to(&mut ret, 1.0)?;
+        Ok(ret)
+    }
+
+    /// Puts this `<length>` or `<percentage>` into `ret`, or error.
+    ///
+    /// `factor` is the sign or multiplicative factor to account for the sign
+    /// (this allows adding and substracting into the return value).
+    fn add_length_or_percentage_to(
+        &self,
+        ret: &mut CalcLengthOrPercentage,
+        factor: CSSFloat)
+        -> Result<(), ()>
+    {
+        match *self {
+            CalcNode::Percentage(pct) => {
+                ret.percentage = Some(ret.percentage.unwrap_or(0.) + pct * factor)
+            }
+            CalcNode::Length(ref l) => {
+                match *l {
+                    NoCalcLength::Absolute(abs) => {
+                        ret.absolute = Some(
+                            ret.absolute.unwrap_or(Au(0)) +
+                            Au::from(abs).scale_by(factor)
+                        );
+                    }
+                    NoCalcLength::FontRelative(rel) => {
+                        match rel {
+                            FontRelativeLength::Em(em) => {
+                                ret.em = Some(ret.em.unwrap_or(0.) + em * factor);
+                            }
+                            FontRelativeLength::Ex(ex) => {
+                                ret.ex = Some(ret.em.unwrap_or(0.) + ex * factor);
+                            }
+                            FontRelativeLength::Ch(ch) => {
+                                ret.ch = Some(ret.ch.unwrap_or(0.) + ch * factor);
+                            }
+                            FontRelativeLength::Rem(rem) => {
+                                ret.rem = Some(ret.rem.unwrap_or(0.) + rem * factor);
+                            }
+                        }
+                    }
+                    NoCalcLength::ViewportPercentage(rel) => {
+                        match rel {
+                            ViewportPercentageLength::Vh(vh) => {
+                                ret.vh = Some(ret.vh.unwrap_or(0.) + vh * factor)
+                            }
+                            ViewportPercentageLength::Vw(vw) => {
+                                ret.vw = Some(ret.vw.unwrap_or(0.) + vw * factor)
+                            }
+                            ViewportPercentageLength::Vmax(vmax) => {
+                                ret.vmax = Some(ret.vmax.unwrap_or(0.) + vmax * factor)
+                            }
+                            ViewportPercentageLength::Vmin(vmin) => {
+                                ret.vmin = Some(ret.vmin.unwrap_or(0.) + vmin * factor)
+                            }
+                        }
+                    }
+                    NoCalcLength::ServoCharacterWidth(..) => unreachable!(),
+                    #[cfg(feature = "gecko")]
+                    NoCalcLength::Physical(physical) => {
+                        ret.mozmm = Some(ret.mozmm.unwrap_or(0.) + physical.0 * factor);
+                    }
+                }
+            }
+            CalcNode::Sub(ref a, ref b) => {
+                a.add_length_or_percentage_to(ret, factor)?;
+                b.add_length_or_percentage_to(ret, factor * -1.0)?;
+            }
+            CalcNode::Sum(ref a, ref b) => {
+                a.add_length_or_percentage_to(ret, factor)?;
+                b.add_length_or_percentage_to(ret, factor)?;
+            }
+            CalcNode::Mul(ref a, ref b) => {
+                match b.to_number() {
+                    Ok(rhs) => {
+                        a.add_length_or_percentage_to(ret, factor * rhs)?;
+                    }
+                    Err(..) => {
+                        let lhs = a.to_number()?;
+                        b.add_length_or_percentage_to(ret, factor * lhs)?;
+                    }
+                }
+            }
+            CalcNode::Div(ref a, ref b) => {
+                let new_factor = b.to_number()?;
+                if new_factor == 0. {
+                    return Err(());
+                }
+                a.add_length_or_percentage_to(ret, factor / new_factor)?;
+            }
+            CalcNode::Angle(..) |
+            CalcNode::Time(..) |
+            CalcNode::Number(..) => return Err(()),
+        }
+
+        Ok(())
+    }
+
+    /// Tries to simplify this expression into a `<time>` value.
+    fn to_time(&self) -> Result<Time, ()> {
+        Ok(match *self {
+            CalcNode::Time(ref time) => time.clone(),
+            CalcNode::Sub(ref a, ref b) => {
+                let lhs = a.to_time()?;
+                let rhs = b.to_time()?;
+                Time::from_calc(lhs.seconds() - rhs.seconds())
+            }
+            CalcNode::Sum(ref a, ref b) => {
+                let lhs = a.to_time()?;
+                let rhs = b.to_time()?;
+                Time::from_calc(lhs.seconds() + rhs.seconds())
+            }
+            CalcNode::Mul(ref a, ref b) => {
+                match b.to_number() {
+                    Ok(rhs) => {
+                        let lhs = a.to_time()?;
+                        Time::from_calc(lhs.seconds() * rhs)
+                    }
+                    Err(()) => {
+                        let lhs = a.to_number()?;
+                        let rhs = b.to_time()?;
+                        Time::from_calc(lhs * rhs.seconds())
+                    }
+                }
+            }
+            CalcNode::Div(ref a, ref b) => {
+                let lhs = a.to_time()?;
+                let rhs = b.to_number()?;
+                if rhs == 0. {
+                    return Err(())
+                }
+                Time::from_calc(lhs.seconds() / rhs)
+            }
+            CalcNode::Number(..) |
+            CalcNode::Length(..) |
+            CalcNode::Percentage(..) |
+            CalcNode::Angle(..) => return Err(()),
+        })
+    }
+
+    /// Tries to simplify this expression into an `Angle` value.
+    fn to_angle(&self) -> Result<Angle, ()> {
+        Ok(match *self {
+            CalcNode::Angle(ref angle) => angle.clone(),
+            CalcNode::Sub(ref a, ref b) => {
+                let lhs = a.to_angle()?;
+                let rhs = b.to_angle()?;
+                Angle::from_calc(lhs.radians() - rhs.radians())
+            }
+            CalcNode::Sum(ref a, ref b) => {
+                let lhs = a.to_angle()?;
+                let rhs = b.to_angle()?;
+                Angle::from_calc(lhs.radians() + rhs.radians())
+            }
+            CalcNode::Mul(ref a, ref b) => {
+                match a.to_angle() {
+                    Ok(lhs) => {
+                        let rhs = b.to_number()?;
+                        Angle::from_calc(lhs.radians() * rhs)
+                    }
+                    Err(..) => {
+                        let lhs = a.to_number()?;
+                        let rhs = b.to_angle()?;
+                        Angle::from_calc(lhs * rhs.radians())
+                    }
+                }
+            }
+            CalcNode::Div(ref a, ref b) => {
+                let lhs = a.to_angle()?;
+                let rhs = b.to_number()?;
+                if rhs == 0. {
+                    return Err(())
+                }
+                Angle::from_calc(lhs.radians() / rhs)
+            }
+            CalcNode::Number(..) |
+            CalcNode::Length(..) |
+            CalcNode::Percentage(..) |
+            CalcNode::Time(..) => return Err(()),
+        })
+    }
+
+    /// Tries to simplify this expression into a `<number>` value.
+    fn to_number(&self) -> Result<CSSFloat, ()> {
+        Ok(match *self {
+            CalcNode::Number(n) => n,
+            CalcNode::Sum(ref a, ref b) => {
+                a.to_number()? + b.to_number()?
+            }
+            CalcNode::Sub(ref a, ref b) => {
+                a.to_number()? - b.to_number()?
+            }
+            CalcNode::Mul(ref a, ref b) => {
+                a.to_number()? * b.to_number()?
+            }
+            CalcNode::Div(ref a, ref b) => {
+                let lhs = a.to_number()?;
+                let rhs = b.to_number()?;
+                if rhs == 0. {
+                    return Err(())
+                }
+                lhs / rhs
+            }
+            CalcNode::Length(..) |
+            CalcNode::Percentage(..) |
+            CalcNode::Angle(..) |
+            CalcNode::Time(..) => return Err(()),
+        })
+    }
+
+    /// Convenience parsing function for integers.
+    pub fn parse_integer(
+        context: &ParserContext,
+        input: &mut Parser)
+        -> Result<CSSInteger, ()>
+    {
+        Self::parse(context, input, CalcUnit::Integer)?
+            .to_number()
+            .map(|n| n as CSSInteger)
+    }
+
+    /// Convenience parsing function for `<length> | <percentage>`.
+    pub fn parse_length_or_percentage(
+        context: &ParserContext,
+        input: &mut Parser)
+        -> Result<CalcLengthOrPercentage, ()>
+    {
+        Self::parse(context, input, CalcUnit::LengthOrPercentage)?
+            .to_length_or_percentage()
+    }
+
+    /// Convenience parsing function for `<length>`.
+    pub fn parse_length(
+        context: &ParserContext,
+        input: &mut Parser)
+        -> Result<CalcLengthOrPercentage, ()>
+    {
+        Self::parse(context, input, CalcUnit::Length)?
+            .to_length_or_percentage()
+    }
+
+    /// Convenience parsing function for `<number>`.
+    pub fn parse_number(
+        context: &ParserContext,
+        input: &mut Parser)
+        -> Result<CSSFloat, ()>
+    {
+        Self::parse(context, input, CalcUnit::Number)?
+            .to_number()
+    }
+
+    /// Convenience parsing function for `<angle>`.
+    pub fn parse_angle(
+        context: &ParserContext,
+        input: &mut Parser)
+        -> Result<Angle, ()>
+    {
+        Self::parse(context, input, CalcUnit::Angle)?
+            .to_angle()
+    }
+
+    /// Convenience parsing function for `<time>`.
+    pub fn parse_time(
+        context: &ParserContext,
+        input: &mut Parser)
+        -> Result<Time, ()>
+    {
+        Self::parse(context, input, CalcUnit::Time)?
+            .to_time()
+    }
+}
diff --git a/components/style/values/specified/length.rs b/components/style/values/specified/length.rs
index e66022d96ec..5c8845a5605 100644
--- a/components/style/values/specified/length.rs
+++ b/components/style/values/specified/length.rs
@@ -17,11 +17,13 @@ use std::ops::Mul;
 use style_traits::ToCss;
 use style_traits::values::specified::AllowedLengthType;
 use stylesheets::CssRuleType;
-use super::{AllowQuirks, Angle, Number, SimplifiedValueNode, SimplifiedSumNode, Time, ToComputedValue};
+use super::{AllowQuirks, Number, ToComputedValue};
 use values::{Auto, CSSFloat, Either, FONT_MEDIUM_PX, HasViewportPercentage, None_, Normal};
 use values::ExtremumLength;
 use values::computed::{ComputedValueAsSpecified, Context};
+use values::specified::calc::CalcNode;
 
+pub use values::specified::calc::CalcLengthOrPercentage;
 pub use super::image::{AngleOrCorner, ColorStop, EndingShape as GradientEndingShape, Gradient};
 pub use super::image::{GradientKind, HorizontalDirection, Image, LengthOrKeyword, LengthOrPercentageOrKeyword};
 pub use super::image::{SizeKeyword, VerticalDirection};
@@ -637,7 +639,10 @@ impl Length {
             },
             Token::Function(ref name) if name.eq_ignore_ascii_case("calc") =>
                 input.parse_nested_block(|input| {
-                    CalcLengthOrPercentage::parse_length(context, input, num_context)
+                    CalcNode::parse_length(context, input)
+                        .map(|calc| {
+                            Length::Calc(num_context, Box::new(calc))
+                        })
                 }),
             _ => Err(())
         }
@@ -700,432 +705,6 @@ impl<T: Parse> Either<Length, T> {
     }
 }
 
-/// A calc sum expression node.
-#[derive(Clone, Debug)]
-pub struct CalcSumNode {
-    /// The products of this node.
-    pub products: Vec<CalcProductNode>,
-}
-
-/// A calc product expression node.
-#[derive(Clone, Debug)]
-pub struct CalcProductNode {
-    /// The values inside this product node.
-    values: Vec<CalcValueNode>
-}
-
-/// A value inside a `Calc` expression.
-#[derive(Clone, Debug)]
-#[allow(missing_docs)]
-pub enum CalcValueNode {
-    Length(NoCalcLength),
-    Angle(CSSFloat),
-    Time(CSSFloat),
-    Percentage(CSSFloat),
-    Number(CSSFloat),
-    Sum(Box<CalcSumNode>),
-}
-
-#[derive(Clone, Copy, PartialEq)]
-#[allow(missing_docs)]
-pub enum CalcUnit {
-    Number,
-    Integer,
-    Length,
-    LengthOrPercentage,
-    Angle,
-    Time,
-}
-
-#[derive(Clone, PartialEq, Copy, Debug, Default)]
-#[cfg_attr(feature = "servo", derive(HeapSizeOf))]
-#[allow(missing_docs)]
-pub struct CalcLengthOrPercentage {
-    pub absolute: Option<Au>,
-    pub vw: Option<CSSFloat>,
-    pub vh: Option<CSSFloat>,
-    pub vmin: Option<CSSFloat>,
-    pub vmax: Option<CSSFloat>,
-    pub em: Option<CSSFloat>,
-    pub ex: Option<CSSFloat>,
-    pub ch: Option<CSSFloat>,
-    pub rem: Option<CSSFloat>,
-    pub percentage: Option<CSSFloat>,
-}
-
-impl CalcLengthOrPercentage {
-    /// Parse a calc sum node.
-    pub fn parse_sum(context: &ParserContext, input: &mut Parser, expected_unit: CalcUnit) -> Result<CalcSumNode, ()> {
-        let mut products = Vec::new();
-        products.push(try!(CalcLengthOrPercentage::parse_product(context, input, expected_unit)));
-
-        loop {
-            let position = input.position();
-            match input.next_including_whitespace() {
-                Ok(Token::WhiteSpace(_)) => {
-                    if input.is_exhausted() {
-                        break; // allow trailing whitespace
-                    }
-                    match input.next() {
-                        Ok(Token::Delim('+')) => {
-                            products.push(try!(CalcLengthOrPercentage::parse_product(context, input, expected_unit)));
-                        }
-                        Ok(Token::Delim('-')) => {
-                            let mut right = try!(CalcLengthOrPercentage::parse_product(context, input, expected_unit));
-                            right.values.push(CalcValueNode::Number(-1.));
-                            products.push(right);
-                        }
-                        _ => {
-                            return Err(());
-                        }
-                    }
-                }
-                _ => {
-                    input.reset(position);
-                    break
-                }
-            }
-        }
-        Ok(CalcSumNode { products: products })
-    }
-
-    fn parse_product(context: &ParserContext, input: &mut Parser, expected_unit: CalcUnit)
-                     -> Result<CalcProductNode, ()> {
-        let mut values = Vec::new();
-        values.push(try!(CalcLengthOrPercentage::parse_value(context, input, expected_unit)));
-
-        loop {
-            let position = input.position();
-            match input.next() {
-                Ok(Token::Delim('*')) => {
-                    values.push(try!(CalcLengthOrPercentage::parse_value(context, input, expected_unit)));
-                }
-                Ok(Token::Delim('/')) if expected_unit != CalcUnit::Integer => {
-                    if let Ok(Token::Number(ref value)) = input.next() {
-                        if value.value == 0. {
-                            return Err(());
-                        }
-                        values.push(CalcValueNode::Number(1. / value.value));
-                    } else {
-                        return Err(());
-                    }
-                }
-                _ => {
-                    input.reset(position);
-                    break
-                }
-            }
-        }
-
-        Ok(CalcProductNode { values: values })
-    }
-
-    fn parse_value(context: &ParserContext, input: &mut Parser, expected_unit: CalcUnit) -> Result<CalcValueNode, ()> {
-        match (try!(input.next()), expected_unit) {
-            (Token::Number(ref value), _) => Ok(CalcValueNode::Number(value.value)),
-            (Token::Dimension(ref value, ref unit), CalcUnit::Length) |
-            (Token::Dimension(ref value, ref unit), CalcUnit::LengthOrPercentage) => {
-                NoCalcLength::parse_dimension(context, value.value, unit).map(CalcValueNode::Length)
-            }
-            (Token::Dimension(ref value, ref unit), CalcUnit::Angle) => {
-                Angle::parse_dimension(value.value, unit).map(|angle| {
-                    CalcValueNode::Angle(angle.radians())
-                })
-            }
-            (Token::Dimension(ref value, ref unit), CalcUnit::Time) => {
-                Time::parse_dimension(value.value, unit).map(|time| {
-                    CalcValueNode::Time(time.seconds())
-                })
-            }
-            (Token::Percentage(ref value), CalcUnit::LengthOrPercentage) =>
-                Ok(CalcValueNode::Percentage(value.unit_value)),
-            (Token::ParenthesisBlock, _) => {
-                input.parse_nested_block(|i| CalcLengthOrPercentage::parse_sum(context, i, expected_unit))
-                     .map(|result| CalcValueNode::Sum(Box::new(result)))
-            },
-            (Token::Function(ref name), _) if name.eq_ignore_ascii_case("calc") => {
-                input.parse_nested_block(|i| CalcLengthOrPercentage::parse_sum(context, i, expected_unit))
-                     .map(|result| CalcValueNode::Sum(Box::new(result)))
-            }
-            _ => Err(())
-        }
-    }
-
-    fn simplify_value_to_number(node: &CalcValueNode) -> Option<CSSFloat> {
-        match *node {
-            CalcValueNode::Number(number) => Some(number),
-            CalcValueNode::Sum(ref sum) => CalcLengthOrPercentage::simplify_sum_to_number(sum),
-            _ => None
-        }
-    }
-
-    fn simplify_sum_to_number(node: &CalcSumNode) -> Option<CSSFloat> {
-        let mut sum = 0.;
-        for ref product in &node.products {
-            match CalcLengthOrPercentage::simplify_product_to_number(product) {
-                Some(number) => sum += number,
-                _ => return None
-            }
-        }
-        Some(sum)
-    }
-
-    fn simplify_product_to_number(node: &CalcProductNode) -> Option<CSSFloat> {
-        let mut product = 1.;
-        for ref value in &node.values {
-            match CalcLengthOrPercentage::simplify_value_to_number(value) {
-                Some(number) => product *= number,
-                _ => return None
-            }
-        }
-        Some(product)
-    }
-
-    fn simplify_products_in_sum(node: &CalcSumNode) -> Result<SimplifiedValueNode, ()> {
-        let mut simplified = Vec::new();
-        for product in &node.products {
-            match try!(CalcLengthOrPercentage::simplify_product(product)) {
-                SimplifiedValueNode::Sum(ref sum) => simplified.extend_from_slice(&sum.values),
-                val => simplified.push(val),
-            }
-        }
-
-        if simplified.len() == 1 {
-            Ok(simplified[0].clone())
-        } else {
-            Ok(SimplifiedValueNode::Sum(Box::new(SimplifiedSumNode { values: simplified })))
-        }
-    }
-
-    #[allow(missing_docs)]
-    pub fn simplify_product(node: &CalcProductNode) -> Result<SimplifiedValueNode, ()> {
-        let mut multiplier = 1.;
-        let mut node_with_unit = None;
-        for node in &node.values {
-            match CalcLengthOrPercentage::simplify_value_to_number(&node) {
-                Some(number) => multiplier *= number,
-                _ if node_with_unit.is_none() => {
-                    node_with_unit = Some(match *node {
-                        CalcValueNode::Sum(ref sum) =>
-                            try!(CalcLengthOrPercentage::simplify_products_in_sum(sum)),
-                        CalcValueNode::Length(ref l) => SimplifiedValueNode::Length(l.clone()),
-                        CalcValueNode::Angle(a) => SimplifiedValueNode::Angle(a),
-                        CalcValueNode::Time(t) => SimplifiedValueNode::Time(t),
-                        CalcValueNode::Percentage(p) => SimplifiedValueNode::Percentage(p),
-                        _ => unreachable!("Numbers should have been handled by simplify_value_to_nubmer")
-                    })
-                },
-                _ => return Err(()),
-            }
-        }
-
-        match node_with_unit {
-            None => Ok(SimplifiedValueNode::Number(multiplier)),
-            Some(ref value) => Ok(value * multiplier)
-        }
-    }
-
-    fn parse_length(context: &ParserContext,
-                    input: &mut Parser,
-                    num_context: AllowedLengthType) -> Result<Length, ()> {
-        CalcLengthOrPercentage::parse(context, input, CalcUnit::Length).map(|calc| {
-            Length::Calc(num_context, Box::new(calc))
-        })
-    }
-
-    fn parse_length_or_percentage(context: &ParserContext, input: &mut Parser) -> Result<CalcLengthOrPercentage, ()> {
-        CalcLengthOrPercentage::parse(context, input, CalcUnit::LengthOrPercentage)
-    }
-
-    #[allow(missing_docs)]
-    pub fn parse(context: &ParserContext,
-                 input: &mut Parser,
-                 expected_unit: CalcUnit) -> Result<CalcLengthOrPercentage, ()> {
-        let ast = try!(CalcLengthOrPercentage::parse_sum(context, input, expected_unit));
-
-        let mut simplified = Vec::new();
-        for ref node in ast.products {
-            match try!(CalcLengthOrPercentage::simplify_product(node)) {
-                SimplifiedValueNode::Sum(sum) => simplified.extend_from_slice(&sum.values),
-                value => simplified.push(value),
-            }
-        }
-
-        let mut absolute = None;
-        let mut vw = None;
-        let mut vh = None;
-        let mut vmax = None;
-        let mut vmin = None;
-        let mut em = None;
-        let mut ex = None;
-        let mut ch = None;
-        let mut rem = None;
-        let mut percentage = None;
-
-        for value in simplified {
-            match value {
-                SimplifiedValueNode::Percentage(p) =>
-                    percentage = Some(percentage.unwrap_or(0.) + p),
-                SimplifiedValueNode::Length(NoCalcLength::Absolute(length)) =>
-                    absolute = Some(absolute.unwrap_or(0.) + Au::from(length).to_f32_px()),
-                SimplifiedValueNode::Length(NoCalcLength::ViewportPercentage(v)) =>
-                    match v {
-                        ViewportPercentageLength::Vw(val) =>
-                            vw = Some(vw.unwrap_or(0.) + val),
-                        ViewportPercentageLength::Vh(val) =>
-                            vh = Some(vh.unwrap_or(0.) + val),
-                        ViewportPercentageLength::Vmin(val) =>
-                            vmin = Some(vmin.unwrap_or(0.) + val),
-                        ViewportPercentageLength::Vmax(val) =>
-                            vmax = Some(vmax.unwrap_or(0.) + val),
-                    },
-                SimplifiedValueNode::Length(NoCalcLength::FontRelative(f)) =>
-                    match f {
-                        FontRelativeLength::Em(val) =>
-                            em = Some(em.unwrap_or(0.) + val),
-                        FontRelativeLength::Ex(val) =>
-                            ex = Some(ex.unwrap_or(0.) + val),
-                        FontRelativeLength::Ch(val) =>
-                            ch = Some(ch.unwrap_or(0.) + val),
-                        FontRelativeLength::Rem(val) =>
-                            rem = Some(rem.unwrap_or(0.) + val),
-                    },
-                // TODO Add support for top level number in calc(). See servo/servo#14421.
-                _ => return Err(()),
-            }
-        }
-
-        Ok(CalcLengthOrPercentage {
-            absolute: absolute.map(Au::from_f32_px),
-            vw: vw,
-            vh: vh,
-            vmax: vmax,
-            vmin: vmin,
-            em: em,
-            ex: ex,
-            ch: ch,
-            rem: rem,
-            percentage: percentage,
-        })
-    }
-
-    #[allow(missing_docs)]
-    pub fn parse_time(context: &ParserContext, input: &mut Parser) -> Result<Time, ()> {
-        let ast = try!(CalcLengthOrPercentage::parse_sum(context, input, CalcUnit::Time));
-
-        let mut simplified = Vec::new();
-        for ref node in ast.products {
-            match try!(CalcLengthOrPercentage::simplify_product(node)) {
-                SimplifiedValueNode::Sum(sum) => simplified.extend_from_slice(&sum.values),
-                value => simplified.push(value),
-            }
-        }
-
-        let mut time = None;
-
-        for value in simplified {
-            match value {
-                SimplifiedValueNode::Time(val) =>
-                    time = Some(time.unwrap_or(0.) + val),
-                _ => return Err(()),
-            }
-        }
-
-        match time {
-            Some(time) => Ok(Time::from_calc(time)),
-            _ => Err(())
-        }
-    }
-
-    #[allow(missing_docs)]
-    pub fn parse_angle(context: &ParserContext, input: &mut Parser) -> Result<Angle, ()> {
-        let ast = try!(CalcLengthOrPercentage::parse_sum(context, input, CalcUnit::Angle));
-
-        let mut simplified = Vec::new();
-        for ref node in ast.products {
-            match try!(CalcLengthOrPercentage::simplify_product(node)) {
-                SimplifiedValueNode::Sum(sum) => simplified.extend_from_slice(&sum.values),
-                value => simplified.push(value),
-            }
-        }
-
-        let mut angle = None;
-        let mut number = None;
-
-        for value in simplified {
-            match value {
-                SimplifiedValueNode::Angle(val) => {
-                    angle = Some(angle.unwrap_or(0.) + val)
-                }
-                // TODO(emilio): This `Number` logic looks fishy.
-                //
-                // In particular, this allows calc(2 - 2) to parse as an
-                // `Angle`, which doesn't seem desired to me.
-                SimplifiedValueNode::Number(val) => {
-                    number = Some(number.unwrap_or(0.) + val)
-                }
-                _ => unreachable!()
-            }
-        }
-
-        match (angle, number) {
-            (Some(angle), None) => Ok(Angle::from_calc(angle)),
-            (None, Some(value)) if value == 0. => Ok(Angle::from_calc(0.)),
-            _ => Err(())
-        }
-    }
-}
-
-impl HasViewportPercentage for CalcLengthOrPercentage {
-    fn has_viewport_percentage(&self) -> bool {
-        self.vw.is_some() || self.vh.is_some() ||
-            self.vmin.is_some() || self.vmax.is_some()
-    }
-}
-
-impl ToCss for CalcLengthOrPercentage {
-    #[allow(unused_assignments)]
-    fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
-        let mut first_value = true;
-        macro_rules! first_value_check {
-            () => {
-                if !first_value {
-                    try!(dest.write_str(" + "));
-                } else {
-                    first_value = false;
-                }
-            };
-        }
-
-        macro_rules! serialize {
-            ( $( $val:ident ),* ) => {
-                $(
-                    if let Some(val) = self.$val {
-                        first_value_check!();
-                        try!(val.to_css(dest));
-                        try!(dest.write_str(stringify!($val)));
-                    }
-                )*
-            };
-        }
-
-        try!(write!(dest, "calc("));
-
-        serialize!(ch, em, ex, rem, vh, vmax, vmin, vw);
-        if let Some(val) = self.absolute {
-            first_value_check!();
-            try!(val.to_css(dest));
-        }
-
-        if let Some(val) = self.percentage {
-            first_value_check!();
-            try!(write!(dest, "{}%", val * 100.));
-        }
-
-        write!(dest, ")")
-    }
-}
-
 /// A percentage value.
 ///
 /// [0 .. 100%] maps to [0.0 .. 1.0]
@@ -1177,8 +756,6 @@ impl Parse for Percentage {
 impl ComputedValueAsSpecified for Percentage {}
 
 /// A length or a percentage value.
-///
-/// TODO(emilio): Does this make any sense vs. CalcLengthOrPercentage?
 #[derive(Clone, PartialEq, Debug)]
 #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
 #[allow(missing_docs)]
@@ -1254,7 +831,7 @@ impl LengthOrPercentage {
                 Ok(LengthOrPercentage::Length(NoCalcLength::from_px(value.value))),
             Token::Function(ref name) if name.eq_ignore_ascii_case("calc") => {
                 let calc = try!(input.parse_nested_block(|i| {
-                    CalcLengthOrPercentage::parse_length_or_percentage(context, i)
+                    CalcNode::parse_length_or_percentage(context, i)
                 }));
                 Ok(LengthOrPercentage::Calc(Box::new(calc)))
             },
@@ -1338,8 +915,7 @@ impl LengthOrPercentage {
     }
 }
 
-/// TODO(emilio): Do the Length and Percentage variants make any sense with
-/// CalcLengthOrPercentage?
+/// Either a `<length>`, a `<percentage>`, or the `auto` keyword.
 #[derive(Clone, PartialEq, Debug)]
 #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
 #[allow(missing_docs)]
@@ -1350,7 +926,6 @@ pub enum LengthOrPercentageOrAuto {
     Calc(Box<CalcLengthOrPercentage>),
 }
 
-
 impl From<NoCalcLength> for LengthOrPercentageOrAuto {
     #[inline]
     fn from(len: NoCalcLength) -> Self {
@@ -1410,7 +985,7 @@ impl LengthOrPercentageOrAuto {
                 Ok(LengthOrPercentageOrAuto::Auto),
             Token::Function(ref name) if name.eq_ignore_ascii_case("calc") => {
                 let calc = try!(input.parse_nested_block(|i| {
-                    CalcLengthOrPercentage::parse_length_or_percentage(context, i)
+                    CalcNode::parse_length_or_percentage(context, i)
                 }));
                 Ok(LengthOrPercentageOrAuto::Calc(Box::new(calc)))
             },
@@ -1462,8 +1037,7 @@ impl LengthOrPercentageOrAuto {
     }
 }
 
-/// TODO(emilio): Do the Length and Percentage variants make any sense with
-/// CalcLengthOrPercentage?
+/// Either a `<length>`, a `<percentage>`, or the `none` keyword.
 #[derive(Clone, PartialEq, Debug)]
 #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
 #[allow(missing_docs)]
@@ -1517,7 +1091,7 @@ impl LengthOrPercentageOrNone {
             }
             Token::Function(ref name) if name.eq_ignore_ascii_case("calc") => {
                 let calc = try!(input.parse_nested_block(|i| {
-                    CalcLengthOrPercentage::parse_length_or_percentage(context, i)
+                    CalcNode::parse_length_or_percentage(context, i)
                 }));
                 Ok(LengthOrPercentageOrNone::Calc(Box::new(calc)))
             },
@@ -1561,8 +1135,6 @@ pub type LengthOrAuto = Either<Length, Auto>;
 
 /// Either a `<length>` or a `<percentage>` or the `auto` keyword or the
 /// `content` keyword.
-///
-/// TODO(emilio): Do the Length and Percentage variants make any sense with
 #[derive(Clone, PartialEq, Debug)]
 #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
 pub enum LengthOrPercentageOrAutoOrContent {
@@ -1596,7 +1168,7 @@ impl LengthOrPercentageOrAutoOrContent {
                 Ok(LengthOrPercentageOrAutoOrContent::Content),
             Token::Function(ref name) if name.eq_ignore_ascii_case("calc") => {
                 let calc = try!(input.parse_nested_block(|i| {
-                    CalcLengthOrPercentage::parse_length_or_percentage(context, i)
+                    CalcNode::parse_length_or_percentage(context, i)
                 }));
                 Ok(LengthOrPercentageOrAutoOrContent::Calc(Box::new(calc)))
             },
diff --git a/components/style/values/specified/mod.rs b/components/style/values/specified/mod.rs
index 45cebecd22b..3062e3bfff0 100644
--- a/components/style/values/specified/mod.rs
+++ b/components/style/values/specified/mod.rs
@@ -16,13 +16,13 @@ use self::url::SpecifiedUrl;
 use std::ascii::AsciiExt;
 use std::f32;
 use std::fmt;
-use std::ops::Mul;
 use style_traits::ToCss;
 use style_traits::values::specified::AllowedNumericType;
 use super::{Auto, CSSFloat, CSSInteger, HasViewportPercentage, Either, None_};
 use super::computed::{self, Context};
 use super::computed::{Shadow as ComputedShadow, ToComputedValue};
 use super::generics::BorderRadiusSize as GenericBorderRadiusSize;
+use values::specified::calc::CalcNode;
 
 #[cfg(feature = "gecko")]
 pub use self::align::{AlignItems, AlignJustifyContent, AlignJustifySelf, JustifyItems};
@@ -34,13 +34,14 @@ pub use self::image::{LengthOrKeyword, LengthOrPercentageOrKeyword, SizeKeyword,
 pub use self::length::AbsoluteLength;
 pub use self::length::{FontRelativeLength, ViewportPercentageLength, CharacterWidth, Length, CalcLengthOrPercentage};
 pub use self::length::{Percentage, LengthOrNone, LengthOrNumber, LengthOrPercentage, LengthOrPercentageOrAuto};
-pub use self::length::{LengthOrPercentageOrNone, LengthOrPercentageOrAutoOrContent, NoCalcLength, CalcUnit};
+pub use self::length::{LengthOrPercentageOrNone, LengthOrPercentageOrAutoOrContent, NoCalcLength};
 pub use self::length::{MaxLength, MinLength};
 pub use self::position::{HorizontalPosition, Position, VerticalPosition};
 
 #[cfg(feature = "gecko")]
 pub mod align;
 pub mod basic_shape;
+pub mod calc;
 pub mod color;
 pub mod grid;
 pub mod image;
@@ -153,96 +154,28 @@ impl ToCss for CSSRGBA {
     }
 }
 
-#[derive(Clone, Debug)]
-#[allow(missing_docs)]
-pub struct SimplifiedSumNode {
-    values: Vec<SimplifiedValueNode>,
-}
-impl<'a> Mul<CSSFloat> for &'a SimplifiedSumNode {
-    type Output = SimplifiedSumNode;
-
-    #[inline]
-    fn mul(self, scalar: CSSFloat) -> SimplifiedSumNode {
-        SimplifiedSumNode {
-            values: self.values.iter().map(|p| p * scalar).collect()
-        }
-    }
-}
-
-#[derive(Clone, Debug)]
-#[allow(missing_docs)]
-pub enum SimplifiedValueNode {
-    Length(NoCalcLength),
-    Angle(CSSFloat),
-    Time(CSSFloat),
-    Percentage(CSSFloat),
-    Number(CSSFloat),
-    Sum(Box<SimplifiedSumNode>),
-}
-
-impl<'a> Mul<CSSFloat> for &'a SimplifiedValueNode {
-    type Output = SimplifiedValueNode;
-
-    #[inline]
-    fn mul(self, scalar: CSSFloat) -> SimplifiedValueNode {
-        match *self {
-            SimplifiedValueNode::Length(ref l) => {
-                SimplifiedValueNode::Length(l.clone() * scalar)
-            },
-            SimplifiedValueNode::Percentage(p) => {
-                SimplifiedValueNode::Percentage(p * scalar)
-            },
-            SimplifiedValueNode::Angle(a) => {
-                SimplifiedValueNode::Angle(a * scalar)
-            },
-            SimplifiedValueNode::Time(t) => {
-                SimplifiedValueNode::Time(t * scalar)
-            },
-            SimplifiedValueNode::Number(n) => {
-                SimplifiedValueNode::Number(n * scalar)
-            },
-            SimplifiedValueNode::Sum(ref s) => {
-                let sum = &**s * scalar;
-                SimplifiedValueNode::Sum(Box::new(sum))
-            },
-        }
-    }
-}
-
-#[allow(missing_docs)]
+/// Parse an `<integer>` value, handling `calc()` correctly.
 pub fn parse_integer(context: &ParserContext, input: &mut Parser) -> Result<Integer, ()> {
     match try!(input.next()) {
         Token::Number(ref value) => value.int_value.ok_or(()).map(Integer::new),
         Token::Function(ref name) if name.eq_ignore_ascii_case("calc") => {
-            let ast = try!(input.parse_nested_block(|i| {
-                CalcLengthOrPercentage::parse_sum(context, i, CalcUnit::Integer)
+            let result = try!(input.parse_nested_block(|i| {
+                CalcNode::parse_integer(context, i)
             }));
 
-            let mut result = None;
-
-            for ref node in ast.products {
-                match try!(CalcLengthOrPercentage::simplify_product(node)) {
-                    SimplifiedValueNode::Number(val) =>
-                        result = Some(result.unwrap_or(0) + val as CSSInteger),
-                    _ => unreachable!()
-                }
-            }
-
-            match result {
-                Some(result) => Ok(Integer::from_calc(result)),
-                _ => Err(())
-            }
+            Ok(Integer::from_calc(result))
         }
         _ => Err(())
     }
 }
 
-#[allow(missing_docs)]
+/// Parse a `<number>` value, handling `calc()` correctly, and without length
+/// limitations.
 pub fn parse_number(context: &ParserContext, input: &mut Parser) -> Result<Number, ()> {
     parse_number_with_clamping_mode(context, input, AllowedNumericType::All)
 }
 
-#[allow(missing_docs)]
+/// Parse a `<number>` value, with a given clamping mode.
 pub fn parse_number_with_clamping_mode(context: &ParserContext,
                                        input: &mut Parser,
                                        clamping_mode: AllowedNumericType)
@@ -255,29 +188,14 @@ pub fn parse_number_with_clamping_mode(context: &ParserContext,
             })
         },
         Token::Function(ref name) if name.eq_ignore_ascii_case("calc") => {
-            let ast = try!(input.parse_nested_block(|i| {
-                CalcLengthOrPercentage::parse_sum(context, i, CalcUnit::Number)
+            let result = try!(input.parse_nested_block(|i| {
+                CalcNode::parse_number(context, i)
             }));
 
-            let mut result = None;
-
-            for ref node in ast.products {
-                match try!(CalcLengthOrPercentage::simplify_product(node)) {
-                    SimplifiedValueNode::Number(val) =>
-                        result = Some(result.unwrap_or(0.) + val),
-                    _ => unreachable!()
-                }
-            }
-
-            match result {
-                Some(result) => {
-                    Ok(Number {
-                        value: result.min(f32::MAX).max(f32::MIN),
-                        calc_clamping_mode: Some(clamping_mode),
-                    })
-                },
-                _ => Err(())
-            }
+            Ok(Number {
+                value: result.min(f32::MAX).max(f32::MIN),
+                calc_clamping_mode: Some(clamping_mode),
+            })
         }
         _ => Err(())
     }
@@ -338,20 +256,23 @@ impl ToComputedValue for Angle {
 
 impl Angle {
     /// Returns an angle with the given value in degrees.
-    pub fn from_degrees(value: CSSFloat) -> Self {
-        Angle { value: computed::Angle::Degree(value), was_calc: false }
+    pub fn from_degrees(value: CSSFloat, was_calc: bool) -> Self {
+        Angle { value: computed::Angle::Degree(value), was_calc: was_calc }
     }
+
     /// Returns an angle with the given value in gradians.
-    pub fn from_gradians(value: CSSFloat) -> Self {
-        Angle { value: computed::Angle::Gradian(value), was_calc: false }
+    pub fn from_gradians(value: CSSFloat, was_calc: bool) -> Self {
+        Angle { value: computed::Angle::Gradian(value), was_calc: was_calc }
     }
+
     /// Returns an angle with the given value in turns.
-    pub fn from_turns(value: CSSFloat) -> Self {
-        Angle { value: computed::Angle::Turn(value), was_calc: false }
+    pub fn from_turns(value: CSSFloat, was_calc: bool) -> Self {
+        Angle { value: computed::Angle::Turn(value), was_calc: was_calc }
     }
+
     /// Returns an angle with the given value in radians.
-    pub fn from_radians(value: CSSFloat) -> Self {
-        Angle { value: computed::Angle::Radian(value), was_calc: false }
+    pub fn from_radians(value: CSSFloat, was_calc: bool) -> Self {
+        Angle { value: computed::Angle::Radian(value), was_calc: was_calc }
     }
 
     #[inline]
@@ -362,7 +283,7 @@ impl Angle {
 
     /// Returns an angle value that represents zero.
     pub fn zero() -> Self {
-        Self::from_degrees(0.0)
+        Self::from_degrees(0.0, false)
     }
 
     /// Returns an `Angle` parsed from a `calc()` expression.
@@ -378,40 +299,55 @@ impl Parse for Angle {
     /// Parses an angle according to CSS-VALUES § 6.1.
     fn parse(context: &ParserContext, input: &mut Parser) -> Result<Self, ()> {
         match try!(input.next()) {
-            Token::Dimension(ref value, ref unit) => Angle::parse_dimension(value.value, unit),
+            Token::Dimension(ref value, ref unit) => {
+                Angle::parse_dimension(value.value,
+                                       unit,
+                                       /* from_calc = */ false)
+            }
             Token::Function(ref name) if name.eq_ignore_ascii_case("calc") => {
-                input.parse_nested_block(|i| CalcLengthOrPercentage::parse_angle(context, i))
-            },
+                input.parse_nested_block(|i| CalcNode::parse_angle(context, i))
+            }
             _ => Err(())
         }
     }
 }
 
 impl Angle {
-    #[allow(missing_docs)]
-    pub fn parse_dimension(value: CSSFloat, unit: &str) -> Result<Angle, ()> {
+    /// Parse an `<angle>` value given a value and an unit.
+    pub fn parse_dimension(
+        value: CSSFloat,
+        unit: &str,
+        from_calc: bool)
+        -> Result<Angle, ()>
+    {
         let angle = match_ignore_ascii_case! { unit,
-            "deg" => Angle::from_degrees(value),
-            "grad" => Angle::from_gradians(value),
-            "turn" => Angle::from_turns(value),
-            "rad" => Angle::from_radians(value),
+            "deg" => Angle::from_degrees(value, from_calc),
+            "grad" => Angle::from_gradians(value, from_calc),
+            "turn" => Angle::from_turns(value, from_calc),
+            "rad" => Angle::from_radians(value, from_calc),
              _ => return Err(())
         };
         Ok(angle)
     }
     /// Parse an angle, including unitless 0 degree.
-    /// Note that numbers without any AngleUnit, including unitless 0
-    /// angle, should be invalid. However, some properties still accept
-    /// unitless 0 angle and stores it as '0deg'. We can remove this and
-    /// get back to the unified version Angle::parse once
+    ///
+    /// Note that numbers without any AngleUnit, including unitless 0 angle,
+    /// should be invalid. However, some properties still accept unitless 0
+    /// angle and stores it as '0deg'.
+    ///
+    /// We can remove this and get back to the unified version Angle::parse once
     /// https://github.com/w3c/csswg-drafts/issues/1162 is resolved.
     pub fn parse_with_unitless(context: &ParserContext, input: &mut Parser) -> Result<Self, ()> {
         match try!(input.next()) {
-            Token::Dimension(ref value, ref unit) => Angle::parse_dimension(value.value, unit),
+            Token::Dimension(ref value, ref unit) => {
+                Angle::parse_dimension(value.value,
+                                       unit,
+                                       /* from_calc = */ false)
+            }
             Token::Number(ref value) if value.value == 0. => Ok(Angle::zero()),
             Token::Function(ref name) if name.eq_ignore_ascii_case("calc") => {
-                input.parse_nested_block(|i| CalcLengthOrPercentage::parse_angle(context, i))
-            },
+                input.parse_nested_block(|i| CalcNode::parse_angle(context, i))
+            }
             _ => Err(())
         }
     }
@@ -579,7 +515,12 @@ impl Time {
     }
 
     /// Parses a time according to CSS-VALUES § 6.2.
-    fn parse_dimension(value: CSSFloat, unit: &str) -> Result<Time, ()> {
+    pub fn parse_dimension(
+        value: CSSFloat,
+        unit: &str,
+        from_calc: bool)
+        -> Result<Time, ()>
+    {
         let seconds = match_ignore_ascii_case! { unit,
             "s" => value,
             "ms" => value / 1000.0,
@@ -588,7 +529,7 @@ impl Time {
 
         Ok(Time {
             seconds: seconds,
-            was_calc: false,
+            was_calc: from_calc,
         })
     }
 
@@ -620,10 +561,10 @@ impl Parse for Time {
     fn parse(context: &ParserContext, input: &mut Parser) -> Result<Self, ()> {
         match input.next() {
             Ok(Token::Dimension(ref value, ref unit)) => {
-                Time::parse_dimension(value.value, &unit)
+                Time::parse_dimension(value.value, &unit, /* from_calc = */ false)
             }
             Ok(Token::Function(ref name)) if name.eq_ignore_ascii_case("calc") => {
-                input.parse_nested_block(|i| CalcLengthOrPercentage::parse_time(context, i))
+                input.parse_nested_block(|i| CalcNode::parse_time(context, i))
             }
             _ => Err(())
         }
@@ -804,7 +745,7 @@ impl Integer {
     }
 
     /// Trivially constructs a new integer value from a `calc()` expression.
-    pub fn from_calc(val: CSSInteger) -> Self {
+    fn from_calc(val: CSSInteger) -> Self {
         Integer {
             value: val,
             was_calc: true,
diff --git a/tests/unit/style/parsing/inherited_box.rs b/tests/unit/style/parsing/inherited_box.rs
index e720035c2e6..f9c3066eb38 100644
--- a/tests/unit/style/parsing/inherited_box.rs
+++ b/tests/unit/style/parsing/inherited_box.rs
@@ -14,14 +14,14 @@ fn image_orientation_longhand_should_parse_properly() {
     assert_eq!(from_image, SpecifiedValue { angle: None, flipped: false });
 
     let flip = parse_longhand!(image_orientation, "flip");
-    assert_eq!(flip, SpecifiedValue { angle: Some(Angle::from_degrees(0.0)), flipped: true });
+    assert_eq!(flip, SpecifiedValue { angle: Some(Angle::zero()), flipped: true });
 
     let zero = parse_longhand!(image_orientation, "0deg");
-    assert_eq!(zero, SpecifiedValue { angle: Some(Angle::from_degrees(0.0)), flipped: false });
+    assert_eq!(zero, SpecifiedValue { angle: Some(Angle::zero()), flipped: false });
 
     let negative_rad = parse_longhand!(image_orientation, "-1rad");
-    assert_eq!(negative_rad, SpecifiedValue { angle: Some(Angle::from_radians(-1.0)), flipped: false });
+    assert_eq!(negative_rad, SpecifiedValue { angle: Some(Angle::from_radians(-1.0, false)), flipped: false });
 
     let flip_with_180 = parse_longhand!(image_orientation, "180deg flip");
-    assert_eq!(flip_with_180, SpecifiedValue { angle: Some(Angle::from_degrees(180.0)), flipped: true });
+    assert_eq!(flip_with_180, SpecifiedValue { angle: Some(Angle::from_degrees(180.0, false)), flipped: true });
 }
diff --git a/tests/unit/style/parsing/length.rs b/tests/unit/style/parsing/length.rs
index 4263f2a08a1..9de042f26ff 100644
--- a/tests/unit/style/parsing/length.rs
+++ b/tests/unit/style/parsing/length.rs
@@ -20,6 +20,7 @@ fn test_calc() {
     assert!(parse(Length::parse, "calc( 1px + 2px )").is_ok());
     assert!(parse(Length::parse, "calc(1px + 2px )").is_ok());
     assert!(parse(Length::parse, "calc( 1px + 2px)").is_ok());
+    assert!(parse(Length::parse, "calc( 1px + 2px / ( 1 + 2 - 1))").is_ok());
 }
 
 #[test]
diff --git a/tests/unit/style/parsing/value.rs b/tests/unit/style/parsing/value.rs
index 643b74ee23a..637a6131912 100644
--- a/tests/unit/style/parsing/value.rs
+++ b/tests/unit/style/parsing/value.rs
@@ -6,7 +6,6 @@ use app_units::Au;
 use parsing::parse;
 use style::values::HasViewportPercentage;
 use style::values::specified::{AbsoluteLength, NoCalcLength, ViewportPercentageLength};
-use style::values::specified::length::{CalcLengthOrPercentage, CalcUnit};
 
 #[test]
 fn length_has_viewport_percentage() {
@@ -15,21 +14,3 @@ fn length_has_viewport_percentage() {
     let l = NoCalcLength::Absolute(AbsoluteLength::Px(Au(100).to_f32_px()));
     assert!(!l.has_viewport_percentage());
 }
-
-#[test]
-fn calc_top_level_number_with_unit() {
-    fn parse_value(text: &str, unit: CalcUnit) -> Result<CalcLengthOrPercentage, ()> {
-        parse(|context, input| CalcLengthOrPercentage::parse(context, input, unit), text)
-    }
-    assert_eq!(parse_value("1", CalcUnit::Length), Err(()));
-    assert_eq!(parse_value("1", CalcUnit::LengthOrPercentage), Err(()));
-    assert_eq!(parse_value("1", CalcUnit::Angle), Err(()));
-    assert_eq!(parse_value("1", CalcUnit::Time), Err(()));
-    assert_eq!(parse_value("1px  + 1", CalcUnit::Length), Err(()));
-    assert_eq!(parse_value("1em  + 1", CalcUnit::Length), Err(()));
-    assert_eq!(parse_value("1px  + 1", CalcUnit::LengthOrPercentage), Err(()));
-    assert_eq!(parse_value("1%   + 1", CalcUnit::LengthOrPercentage), Err(()));
-    assert_eq!(parse_value("1rad + 1", CalcUnit::Angle), Err(()));
-    assert_eq!(parse_value("1deg + 1", CalcUnit::Angle), Err(()));
-    assert_eq!(parse_value("1s   + 1", CalcUnit::Time), Err(()));
-}
diff --git a/tests/unit/style/properties/serialization.rs b/tests/unit/style/properties/serialization.rs
index 5f2ecdaf7ca..0e89e22cde4 100644
--- a/tests/unit/style/properties/serialization.rs
+++ b/tests/unit/style/properties/serialization.rs
@@ -1043,19 +1043,19 @@ mod shorthand_serialization {
         #[test]
         fn transform_skew() {
             validate_serialization(
-                &SpecifiedOperation::Skew(Angle::from_degrees(42.3), None),
+                &SpecifiedOperation::Skew(Angle::from_degrees(42.3, false), None),
                 "skew(42.3deg)");
             validate_serialization(
-                &SpecifiedOperation::Skew(Angle::from_gradians(-50.0), Some(Angle::from_turns(0.73))),
+                &SpecifiedOperation::Skew(Angle::from_gradians(-50.0, false), Some(Angle::from_turns(0.73, false))),
                 "skew(-50grad, 0.73turn)");
             validate_serialization(
-                &SpecifiedOperation::SkewX(Angle::from_radians(0.31)), "skewX(0.31rad)");
+                &SpecifiedOperation::SkewX(Angle::from_radians(0.31, false)), "skewX(0.31rad)");
         }
 
         #[test]
         fn transform_rotate() {
             validate_serialization(
-                &SpecifiedOperation::Rotate(Angle::from_turns(35.0)),
+                &SpecifiedOperation::Rotate(Angle::from_turns(35.0, false)),
                 "rotate(35turn)"
             )
         }